The present application relates to a stacked nonaqueous electrolyte battery, a manufacturing method thereof, and a staking apparatus. More particularly, the application relates to a stacked nonaqueous electrolyte battery whose battery quality and performance are enhanced by preventing electrodes from deviating from their proper positions in stacking the electrodes, and a manufacturing method thereof and a stacking apparatus therefor.
As electronic equipment, such as cellular phones and notebook personal computers, goes further cordless and portable in recent years, thickness-, size-, and weight-reduced portable electronic apparatuses have been developed one after another. Furthermore, their power consumption is on the increase due to diversification of types and functions, and this demands batteries with even higher-capacity and in even lighter weight as their energy source. Accordingly, in order to meet this demand, stacked nonaqueous electrolyte batteries, inter alia, various types of lithium ion secondary batteries utilizing the doping/dedoping of lithium ions have been proposed.
In some of these lithium ion secondary batteries, in order to achieve their thickness reduction, a stacked type is used in which a plurality of anodes and cathodes are stacked through separators alternately. In such a battery, at a portion where an anode 1 having anode active material layers 1a formed on both surfaces of an anode current collector 1b is opposed to a cathode 2 having cathode active material layers 2a formed on both surfaces of a cathode current collector 2b through a separator 3, the cathode 2 is larger than the anode 1, and the separator 3 has a length equal to or larger than the cathode 2 as shown in FIG. 1A. In this structure, lithium ions pass through the separator 3 to charge and discharge the battery normally.
However, when the anode 1 is larger than the separator 3 and thus opposed to the cathode 2 as shown in FIG. 1B, a flow of ions not passing through the separator 3 such as shown by dashed lines is produced at a portion where the anode 1 is directly opposed to the cathode 2, addressing issues such as short-circuits and abnormal heat generation in the battery. Furthermore, as shown in FIG. 1C, when the anode 1 is larger than not only the separator 3 but also the cathode 2, lithium 4 is deposited on an edge portion of the cathode 2 and dendrites are formed, so that short-circuits are caused
Thus, since deviation in any of the anode 1, the cathode 2, and the separator 3 greatly affects the quality of the battery, it is required to prevent the anode 1 and the cathode 2 from being directly opposed to each other due to deviation in internal components of the battery when shock is applied to the battery during or after its manufacturing.
Accordingly, a sealed type sheet-shaped lithium battery such as disclosed in Japanese Unexamined Patent Application Publication No. 10-172565 (hereinafter referred to as “Patent Document 1”) has been proposed. In this battery, at least one of an anode and a cathode is housed in a bag-shaped separator in which edge portions are welded, and stacked such as shown in FIG. 2. It is noted in FIG. 2 that a plurality of anodes 1 and cathodes 2 are stacked and shown by omitting a packaging material of the battery.
Furthermore, in addition to the battery having a structure such as disclosed in Patent Document 1, there have been proposed, e.g., a battery having a spirally wound stacked longitudinal sectional structure in which stacked electrode bodies 4 each having an anode 1 and a cathode 2 laminated through a separator 3 are stacked while spirally wound by another sheet of separator 3 such as shown in FIG. 3, and a battery having a folded longitudinal sectional structure in which an anode 1 and a cathode 2 are inserted alternately into spaces of a zigzag-folded separator 3 such as shown in FIG. 4.
However, in the battery disclosed in Patent Document 1 in which at least one of the anode and the cathode is housed in the bag-shaped separator, an expensive sealing apparatus with high positioning accuracy is required in order to ensure a small welding margin of, e.g., about 3 mm to 4 mm at each edge portion of the separator, thereby increasing manufacturing costs. In addition, the electrodes may not be formed larger in size due to the welding margins, which limits the enhancement in battery capacity.
Furthermore, in the above-mentioned battery having the spirally wound stacked or the folded longitudinal sectional structure, each electrode is inserted between separators with some clearance, so that the electrode is held only with contact forces from the vertically adjacent electrodes. This may loosen the hold of the electrode in position and cause the electrode to deviate from its proper position when shock is applied, making it likely to impair the quality of the battery. Furthermore, for these batteries, the separator 3 may be necessary to be folded in a special manner, and this entails expensive equipment.
Furthermore, in a simple configuration in which anodes/cathodes and separators are alternately stacked, respectively, extraneous matter may enter from the interface between a separator and an anode/cathode, making it likely also to block battery reactions to impair the quality and safety of the battery.